An electrical pump assembly (ESP) of the type used in hydrocarbon producing wells includes a rotary pump coupled to an electrical motor by a seal section. The assembly may also include a gas separator. The pump may be a centrifugal pump with a large number of stages, each stage having an impeller and diffuser. Alternately, the pump may be a progressing cavity pump. The motor has a stator with a central longitudinal cavity containing a rotor mounted to a drive shaft. Because of the length of the motor, radial bearings are located between sections of the rotor to radially stabilize the shaft.
Various types of radial bearings are employed. One type of radial bearing has an inner sleeve mounted to the shaft for rotation with the shaft. A carrier body surrounds the inner sleeve and may be in sliding contact with the inner sleeve. Alternately, an outer sleeve my be located between the carrier body and the inner sleeve. An anti-rotation member on the outer diameter of the carrier body frictionally or positively engages an inner diameter surface of the stator to prevent the carrier body from rotating. Elastomers may be located between the carrier body and the outer sleeve to prevent rotation of the outer sleeve and dampen vibration of the shaft.
The carrier body and the sleeve are typically formed of different materials with different coefficients of expansion (CTE). Thermal expansion causes the annular space between the carrier body and the outer sleeve to change, either increasing or decreasing. The elastomers between the carrier body and the outer sleeve will compensate for the thermal growth and prevent the outer sleeve from rotating. However, some wells are too hot for elastomers, particularly steam assisted gravity type (SAGD) wells in Canada. The temperatures may be as high as 575 degrees F.